In a typical automatic transmission, a fluid coupling or torque converter is used to transfer power from the engine to the transmission. A typical torque converter includes an impeller linked to the crankshaft of the engine, and a turbine linked to the input shaft of the transmission. The impeller and turbine are mounted face-to-face within a common housing that is filled with transmission fluid. The impeller and turbine include a series of vanes or blades that rotate about a central axis. As the engine operates, the crankshaft rotates the impeller, thereby causing the fluid contained within the housing to circulate. The moving fluid strikes the blades of the turbine, which causes it to rotate. The rotating turbine imparts rotational movement to the input shaft of the transmission.
The torque converter differs from a fluid coupling in that it multiplies torque transmission. This is achieved by positioning a stator between the turbine and impeller to control the flow of returning fluid from the turbine. The stator includes a series of blades that redirect the fluid to strike the blades of the impeller at an angle that promotes rotation of the impeller. Accordingly, some of the energy of the moving fluid is returned to the impeller.
Because the turbine operates in the powerflow path of the vehicle drive terrain, it must have significant structural integrity to handle the torque requirements. Accordingly, torque converter turbines are typically manufactured from stamped steel to provide the needed strength.